The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
In any device in which air or other fluid moves across a surface, there is turbulence within the boundary layer between the mean flow and the surface, especially when the airflow in a passageway becomes faster in speed. In some instances that turbulence is desirable, and in other instances that turbulence can be problematic.
In speaker port ducts, microphones, and musical instruments passageways, turbulence and associated vortex shedding is a cause of acoustical noise and unwanted distortions. The problem has been addressed to some extent by using larger diameter port ducts, this will help with limiting acoustical compression, but this will make the overall speaker box size larger. See e.g., Maximizing Performance from Loudspeaker Ports, Salvatti, Alex; Devantier, Allan; Button, Douglas J., JAES Volume 50 Issue 1/2 pp. 19-45; February 2002. But larger port bores do not eliminate turbulence within the boundary layer. The problem has also been addressed to some extent by using structures on the surface of the flaring. See for example, U.S. Pat. No. 6,019,188 to Nevill. But none of those technologies adequately addresses the root problem of distortions that a port duct has on a complex sound wave moving through or over a turbulent boundary layer.
Salvatti and Nevill, and all publications referenced herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
Thus, there is still a need for systems and methods that reduce distortion and noise/or improve other sound qualities of speakers, musical instruments, microphones and other devices having an auditorily important acoustical boundary layer.